/**
 * 倒计时
 * @param i 秒数
 */
function countdown(i) {
    var btn = document.getElementById("submit");
    i--;
    if (i == 0) {
        btn.innerHTML = "提交审核";
        btn.disabled = false
    } else {
        btn.innerHTML="等待(" + i + ")秒后可以重新操作" ;
        setTimeout("countdown(" + i + ")", 1000)
    }
}